Unit III: Endocrine & Digestive System Lecture Objectives and Study Guide
Chapter 16: Endocrine System
Functions of the Endocrine System
The endocrine system regulates numerous bodily functions through the secretion of hormones. Major functions include:
Metabolism regulation
Growth and development
Tissue function
Sexual function
Reproduction
Sleep and mood regulation
Comparison of Endocrine and Nervous Systems
Endocrine System:
Uses hormones to send messages
Slower response time
Long-lasting effects
Nervous System:
Uses neurotransmitters to transmit signals
Fast response time
Short-lived effects
Hormones vs. Neurotransmitters:
Hormones are released into the bloodstream and can affect distant targets.
Neurotransmitters act locally at synaptic junctions.
Definition of Hormones and Classifications
Hormone: A chemical messenger produced by endocrine glands and secreted into the bloodstream, which regulates physiological processes.
Three Chemical Classifications:
Peptide/Protein Hormones:
Comprised of amino acids. Example: insulin.
Steroid Hormones:
Derived from cholesterol. Example: cortisol.
Amine Hormones:
Derived from amino acids. Example: epinephrine.
Free vs. Transport Protein-Bound Hormones
Free Hormones:
Circulate in the bloodstream without being bound to proteins.
Example: thyroid hormones typically exist in a free state.
Protein-Bound Hormones:
Bound to transport proteins, which help in transport and extend the hormone’s half-life.
Example: testosterone and cortisol usually exist in protein-bound form.
Fixed vs. Mobile Receptor Models
Fixed Receptors:
Located on the cell membrane and cannot move. Utilized by peptide and most amine hormones.
Mobile Receptors:
Located within the cell and can move across the membrane. Utilized by steroid hormones.
Second Messenger Systems:
Process initiated by hormone binding that results in activation of secondary messenger molecules within the cell.
Examples: cyclic AMP (cAMP) for peptide hormones.
Negative vs. Positive Feedback Systems
Negative Feedback:
A process that counteracts a change in a physiological variable, stabilizing the system. Example: regulation of blood glucose levels.
Positive Feedback:
A process that amplifies a change or increase in function. Example: oxytocin during childbirth.
Hypothalamus and Pituitary Gland Relationship
Anatomical Relationship:
Connected by the infundibulum.
Functional Relationship:
The hypothalamus secretes regulatory factors that control the anterior pituitary.
Adenohypophysis vs. Neurohypophysis:
Adenohypophysis: Anterior pituitary; releases hormones such as ACTH and TSH.
Neurohypophysis: Posterior pituitary; stores and releases hormones like ADH and oxytocin.
Endocrine Glands and Their Secretions
Hypothalamus: Secretes regulatory hormones.
Pancreas (Islets of Langerhans): Secretes insulin and glucagon.
Anterior Pituitary (Adenohypophysis): Secretes hGH, PRL, TSH, ACTH, FSH, LH, MSH.
Ovaries/Testes: Secrete estrogen, progesterone, testosterone.
Posterior Pituitary (Neurohypophysis): Secretes ADH, oxytocin.
Kidneys: Secrete erythropoietin, calcitriol.
Thyroid Gland: Secretes thyroxin (T4), triiodothyronine (T3), calcitonin.
Pineal Gland: Secretes melatonin.
Parathyroid Glands: Secretes parathyroid hormone (PTH).
Thymus: Secretes thymosin and thymopoietin.
Adrenal Cortex & Medulla: Secrete aldosterone, cortisol, epinephrine, norepinephrine.
Heart: Secretes atrial natriuretic peptide (ANP).
Hormones: Classification, Production, Target, Function
Hypothalamic Regulatory Factors:
Classification: Peptide
Site of Production: Hypothalamus
Target Cells: Anterior pituitary
Function: Regulate anterior pituitary hormone secretion.
Human Growth Hormone (hGH):
Classification: Protein
Site of Production: Anterior pituitary
Target Cells: All body tissues
Function: Stimulates growth and metabolism.
Prolactin (PRL):
Classification: Protein
Site of Production: Anterior pituitary
Target Cells: Mammary glands
Function: Stimulates milk production.
Thyroid Stimulating Hormone (TSH):
Classification: Glycoprotein
Site of Production: Anterior pituitary
Target Cells: Thyroid gland
Function: Stimulates thyroid hormone production.
Adrenocorticotropic Hormone (ACTH):
Classification: Peptide
Site of Production: Anterior pituitary
Target Cells: Adrenal cortex
Function: Stimulates cortisol production.
Follicle Stimulating Hormone (FSH):
Classification: Glycoprotein
Site of Production: Anterior pituitary
Target Cells: Ovaries and testes
Function: Stimulates gamete production.
Luteinizing Hormone (LH):
Classification: Glycoprotein
Site of Production: Anterior pituitary
Target Cells: Ovaries and testes
Function: Stimulates sex hormone production.
Melanocyte Stimulating Hormone (MSH):
Classification: Peptide
Site of Production: Anterior pituitary
Target Cells: Skin
Function: Stimulates melanin production.
Antidiuretic Hormone (ADH):
Classification: Peptide
Site of Production: Posterior pituitary
Target Cells: Kidneys
Function: Promotes water retention.
Oxytocin (OT):
Classification: Peptide
Site of Production: Posterior pituitary
Target Cells: Uterus and mammary glands
Function: Initiates labor and milk ejection.
Melatonin:
Classification: Amine
Site of Production: Pineal gland
Target Cells: Brain
Function: Regulates circadian rhythms.
Thyroxin (T4) & Triiodothyronine (T3):
Classification: Amine
Site of Production: Thyroid gland
Target Cells: All body tissues
Function: Regulate metabolism.
Calcitonin:
Classification: Peptide
Site of Production: Thyroid gland
Target Cells: Bones
Function: Lowers blood calcium levels.
Parathyroid Hormone (PTH):
Classification: Peptide
Site of Production: Parathyroid glands
Target Cells: Bones, kidneys, intestines
Function: Raises blood calcium levels.
Thymosin:
Classification: Peptide
Site of Production: Thymus
Target Cells: T-cells
Function: Promotes T-cell development.
Thymopoietin:
Classification: Peptide
Site of Production: Thymus
Target Cells: T-cells
Function: Stimulates T-cell maturation.
Epinephrine/Norepinephrine:
Classification: Amine
Site of Production: Adrenal medulla
Target Cells: Various
Function: Initiates fight-or-flight response.
Aldosterone (Mineral Corticoids):
Classification: Steroid
Site of Production: Adrenal cortex
Target Cells: Kidneys
Function: Regulates sodium and potassium balance.
Cortisol (Glucocorticoids):
Classification: Steroid
Site of Production: Adrenal cortex
Target Cells: Various
Function: Regulates metabolism and stress response.
Dehydroepiandrosterone (DHEA):
Classification: Steroid
Site of Production: Adrenal cortex
Target Cells: Various
Function: Precursor for sex hormones.
Insulin:
Classification: Peptide
Site of Production: Pancreas
Target Cells: Various
Function: Lowers blood glucose levels.
Glucagon:
Classification: Peptide
Site of Production: Pancreas
Target Cells: Liver
Function: Raises blood glucose levels.
Testosterone:
Classification: Steroid
Site of Production: Testes
Target Cells: Various
Function: Regulates male reproductive functions.
Calcitriol:
Classification: Steroid
Site of Production: Kidneys
Target Cells: Intestines
Function: Increases calcium absorption.
Progesterone (PRO):
Classification: Steroid
Site of Production: Ovaries
Target Cells: Uterus
Function: Prepares uterus for pregnancy.
Chapter 23: Digestive System
Definitions
Metabolism: The sum of all biochemical processes that occur within an organism for maintaining life.
Anabolism: The synthesis of complex molecules from simpler ones, generally requiring energy.
Catabolism: The breakdown of complex molecules into simpler ones, usually releasing energy.
Organic Molecules
Protein:
Components: Amino acids
Food Sources: Meat, dairy, legumes
Function: Tissue building and repair, enzymes, hormones
Carbohydrate:
Components: Simple sugars (monosaccharides)
Food Sources: Grains, fruits, vegetables
Function: Primary energy source
Nucleic Acids:
Components: Nucleotides
Food Sources: Meats, grains, and beans
Function: Genetic information storage
Lipid/Triglyceride:
Components: Fatty acids and glycerol
Food Sources: Oils, butter, nuts
Function: Long-term energy storage, cell membrane structure
Hydrolysis Reactions: The process whereby water is used to break chemical bonds, often during digestion to convert food into absorbable units.
Functions of the Digestive System
Ingestion: Taking in food.
Digestion: The mechanical and chemical breakdown of food.
Absorption: The uptake of nutrients from the digestive tract into the blood.
Elimination: The excretion of indigestible substances from the body.
Histology of Digestive Organs
Four Major Histological Layers:
Mucosa: Innermost layer; has epithelial cells for secretion and absorption.
Submucosa: Contains connective tissues, blood vessels, and neurons; supports mucosa.
Muscularis Externa: Responsible for peristalsis; has smooth muscle layers.
Serosa: Outermost layer; a protective layer for the digestive organs.
Sublayers: In the mucosa, includes epithelium, lamina propria, and muscularis mucosae.
Peritoneal Structures
Visceral Peritoneum: Covers organs.
Parietal Peritoneum: Lines the abdominal cavity.
Mesentery Proper: Supports small intestines.
Greater Omentum: A fold of peritoneum that hangs from the stomach.
Lesser Omentum: Connects the stomach to the liver.
Falciform Ligament: Attaches the liver to the anterior abdominal wall.
Mesocolon: Attaches the colon to the posterior abdominal wall.
Digestive Enzymes
Salivary Amylase (Ptyalin):
Site of Production: Salivary glands
Site of Action: Mouth
Function: Begins carbohydrate digestion
Substrate(s): Starch
Product(s): Maltose
Pancreatic Amylase:
Site of Production: Pancreas
Site of Action: Small intestine
Function: Completes carbohydrate digestion
Substrate(s): Starch
Product(s): Maltose, glucose
Pepsin:
Site of Production: Stomach (from pepsinogen)
Site of Action: Stomach
Function: Begins protein digestion
Substrate(s): Proteins
Product(s): Peptides
Trypsin:
Site of Production: Pancreas
Site of Action: Small intestine
Function: Continues protein digestion
Substrate(s): Proteins
Product(s): Peptides
Chymotrypsin:
Site of Production: Pancreas
Site of Action: Small intestine
Function: Continues protein digestion
Substrate(s): Proteins
Product(s): Peptides
Sucrase:
Site of Production: Small intestine
Site of Action: Small intestine
Function: Sugar digestion
Substrate(s): Sucrose
Product(s): Glucose, fructose
Brush Border Nuclease:
Site of Production: Small intestine
Site of Action: Small intestine
Function: Digests nucleic acids
Substrate(s): RNA, DNA
Product(s): Nucleotides
Pancreatic Lipase:
Site of Production: Pancreas
Site of Action: Small intestine
Function: Fat digestion
Substrate(s): Triglycerides
Product(s): Fatty acids, glycerol
Lingual Lipase:
Site of Production: Salivary glands
Site of Action: Mouth
Function: Begins fat digestion
Substrate(s): Triglycerides
Product(s): Fatty acids, glycerol
Hormonal Control of the Digestive System
Gastrin:
Site of Production: Stomach
Stimulus: Food intake
Target Organ(s): Stomach
Function: Stimulates secretion of gastric acids.
GIP (Gastric Inhibitory Peptide):
Site of Production: Small intestine
Stimulus: Fat in the intestine
Target Organ(s): Stomach
Function: Inhibits gastric motility.
Secretin:
Site of Production: Small intestine
Stimulus: Acidic chyme
Target Organ(s): Pancreas
Function: Stimulates bicarbonate secretion.
Cholecystokinin (CCK):
Site of Production: Small intestine
Stimulus: Fatty acids
Target Organ(s): Gallbladder, pancreas
Function: Stimulates bile release and enzyme secretion.
Leptin:
Site of Production: Adipose tissue
Stimulus: Increased fat storage
Target Organ(s): Hypothalamus
Function: Regulates energy balance and appetite.
Ghrelin:
Site of Production: Stomach
Stimulus: Fasting
Target Organ(s): Hypothalamus
Function: Stimulates hunger.
Nervous System Role in Digestion
Vagus Nerve:
Major role in the parasympathetic control of digestion, stimulating gastric secretions and peristalsis.
Submucosal Plexus:
Involved in regulating digestive secretions and blood flow in the gut.
Myenteric Plexus:
Controls gastrointestinal motility, facilitating peristaltic movements through muscle contractions.
Phases of Digestive Activity
Cephalic Phase:
Triggered by the sight, smell, taste, or thought of food, initiating salivation and gastric secretions.
Gastric Phase:
Begins when food enters the stomach, further stimulating gastric secretions and motility.
Intestinal Phase:
Initiated as chyme enters the small intestine, promoting nutrient absorption and secretion.
Definitions of Digestive Terms
Peristalsis: Involuntary contractions that move food through the digestive tract.
Segmentation: Rhythmic contractions of the circular muscles in the intestine, mixing food.
Deglutition: The act of swallowing.
Mastication: The process of chewing food.
Chyme: Semi-liquid mass of partially digested food that moves from the stomach to the intestine.
Feces: Waste matter expelled from the digestive tract.
Bolus: A rounded mass of chewed food ready to be swallowed.
Digestive System Sphincters and Valves
Cardiac (Gastro-esophageal) Sphincter: Controls food entry from the esophagus to the stomach.
Pyloric Sphincter: Controls chyme entry from the stomach into the small intestine.
Anal Sphincter: Controls feces evacuation from the rectum.
Ileocecal Valve: Controls passage from the small intestine to the large intestine.
Hepatopancreatic Sphincter (Sphincter of Oddi): Regulates bile and pancreatic juice entry into the small intestine.
Digestive Organs and Their Functions
The digestive organs include the mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, and gallbladder, each with specific roles in digestion and nutrient absorption.
Enteric Nervous System
A complex network of neurons that governs the function of the gastrointestinal system. Often referred to as the "second brain" due to its autonomy in regulating digestive processes.
Bile Production and Function
Production Site: Liver
Storage Site: Gallbladder
Function: Aids in the emulsification and digestion of fats.
Bile Duct System Components:
Cystic Duct: Connects the gallbladder to the common bile duct.
Hepatic Bile Ducts: Carry bile from the liver.
Common Bile Duct: Transports bile to the duodenum.
Pancreatic Duct: Delivers pancreatic juices to the small intestine.
Hepatopancreatic Ampulla: The junction where bile and pancreatic juices combine before entering the duodenum.
Fasting and Absorptive States
Fasting State: Period when nutrient absorption is not occurring; the body utilizes stored glycogen.
Absorptive State: Period post-meal when nutrients are being absorbed; insulin facilitates glucose uptake into cells.
Glycogen: The storage form of glucose in the liver and muscles.
Glucose: A simple sugar and primary energy source for cells.
Glycogenesis: The process of converting glucose into glycogen for storage.
Glycogenolysis: The breakdown of glycogen into glucose when energy is needed.
Gluconeogenesis: The formation of glucose from non-carbohydrate sources, primarily in the liver.
Autonomic Nervous System Relationship: Regulates the body’s metabolism during the fasting and absorptive states.
Metabolism and Energy Terms
Calorie: A unit of energy defined as the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius.
BMR (Basal Metabolic Rate): The rate at which the body expends energy at rest to maintain basic physiological functions.
ATP (Adenosine Triphosphate): The primary energy carrier in all living organisms.
Aerobic Respiration: The process of producing cellular energy involving oxygen.
Deamination: The removal of an amino group from an amino acid, resulting in the formation of ammonia and a keto acid.
Urea Cycle: A series of chemical reactions occurring in the liver that convert ammonia into urea for excretion.
Major Vitamins and Their Functions
Vitamin A: Vision and immune function.
Thiamine (B1): Energy metabolism and nerve function.
Riboflavin (B2): Energy production and cellular function.
Niacin (B3): DNA repair and metabolism of carbohydrates, fats, and proteins.
Vitamin B6: Amino acid metabolism and neurotransmitter synthesis.
Vitamin B12: Red blood cell formation and nervous system maintenance.
Vitamin C: Antioxidant function and collagen synthesis.
Vitamin D: Calcium absorption and bone health.
Vitamin E: Antioxidant that protects cell membranes.
Folate: DNA synthesis and repair, and cell division.
Vitamin K: Blood clotting and bone metabolism.
Major Minerals and Their Functions
Sodium: Regulates fluid balance and blood pressure.
Potassium: Essential for muscle contraction and nerve function.
Chloride: Helps maintain fluid balance and stomach acidity.
Calcium: Vital for bone health and muscle function.
Phosphorus: Important for energy production and bone mineralization.
Iron: Crucial for oxygen transport in hemoglobin.
Zinc: Supports immune function and wound healing.